Butterfly Mesogens Based on Carbazole, Fluorene or Fluorenone: Mesomorphous, Gelling, Photophysical, and Photoconductive Properties

We report a straightforward and generic synthesis of several new series of annulated pi-extended poly-(hetero)aromatic hydrocarbons (PAH), with carbazole, fluorene and fluorenone central building blocks by the Suzuki-Miyaura/Scholl tandem reactions. The corresponding series of ditriphenylene discogens with a carbazole or a fluorenone central core, respectively, possess hexagonal columnar mesophases with broad mesophase ranges and high clearing points, as well as demonstrate a strong aggregation tendency in organic solvents as supergelators. The laterally-substituted ditriphenylene mesogens based on dimethyl-fluorene core exhibit a rich polymorphism with rectangular and hexagonal columnar mesophases from low temperatures onward, whereas their dioctyl-fluorene homologues melt directly into the isotropic liquid without showing mesophases. These latter family of compounds are luminescent with very high fluorescent quantum yields, of around 70 % in solution, and show outstanding photocurrent behavior with charge carrier mobility in the 10(-2) cm(2) V-1 s(-1) range, as measured by photocurrent transient time-of-flight (TOF) technique. This straightforward molecular design and simple synthetic strategy proved to be both potent and resilient, and could be generally applied to the fabrication of a great variety of other heteroarene molecular systems as organic semiconductors and electroluminescent materials for potentially low-cost applications.

Automated summary

A straightforward synthetic strategy using Suzuki-Miyaura/Scholl tandem reactions was employed to synthesize new series of annulated pi-extended poly-(hetero)aromatic hydrocarbons with carbazole, fluorene, and fluorenone central building blocks. The resulting compounds demonstrated strong aggregation tendencies in organic solvents and exhibited a wide range of liquid crystal phases, as well as high fluorescent quantum yields and excellent photocurrent behavior. This approach provides a potent and resilient method for the fabrication of various heteroarene molecular systems with potential applications in organic semiconductors and electroluminescent materials.